The Locomotive Of Today

The Tender, Brakes, etc.: Double Engines. 177 the branch pipes on each side, but when the biast orifice is closed by the shutting together of the flaps, the bevelled edges of these latter meet and form a V by which the steam is deflected to either side branch pipe. In the drawing the valves are represented as covering the side outlets, and pro- viding for a free opening up the biast pipe. The levers outside are shown in dotted lines; they are each provided with a long slotted pin hole and a forked end to the pull rod has a pin through it and both the levers, pulling this rod upwards brings the levers together, and consequently the valves. A spindle above reaches across from a guide on the smokebox wrapper to another upon the biast pipe, and has suitable levers upon it for attachment of the outside rod from the cab, and the inside pull rod to the valve levers. Balance weights are sometimes fitted to Help in moving the valves, but are not always considered necessary. When very severe gradients and sharp curves make it difficult to design a suitable engine owing to the inconvenient length that would be necessary to carry weight enough for adhesion, double engines have been employed. The best known of these, perhaps, is the “Fairlie” type, which has two groups of driving wheels arranged in swivelling frames or bogies, each group being coupled and provided with separate cylinders and crank axles. By these means very powerful engines can be made with the weight well distributed over a long and flexible wheel base. The boiler has one or two fire- boxes at the centre and two barreis with tubes leading each way—to the front and the back. Two chimneys and domes are also provided. The firing is done through a side door or doors, and tlie fireman rides upon that side of the engine, the driver having all his levers, gear, etc., upon the opposite side. For heavy mountain service many modifications of the ordinary adhesion locomotive are to be met with. One system provides an adclitional small pair of cylinders and drivers equipped with mechanism for raising and lowering, so that when ordinary roads are being negotiated the engine works as usual, but when steep banks, or exceptionally heavy loads are to be worked, the auxiliary wheels are pressed down to the rails and steam admitted to the extra cylinders, giving additional power to assist in overcoming the trouble. The raising and lowering is performed either by steam, air, or vacuum, and varying weights can be put upon the wheels. As one of the chief constituents of the power of a locomotive to haul a load is its boiler, and such arrangements as this make no extra provision there, these curiosities are not to be commended. 12